In six growth hormone-sufficient patients of a pilot study, we have shown synchronicity between nocturnal fluctuations of growth hormone (GH) and PICP, a serum marker of biosynthesis of type I procollagen. We also discovered down-regulation of PICP coincident with the AM rise in cortisol (F). We now intend to further clarify the modulation of PICP by 1. The physiological fluctuation of endogenous GH and F; 2) The administration of exogenous GH; and by(3) The inhibition of endogenous F. We will include profibrotic hormone aldosterone, which also shows diurnal variablility in both GH-deficient and GH sufficient patients.